It has heretofore been proposed that closures be provided for containers wherein the closures on the container by an integral hinge. Conventionally, such closures rely on tension on the hinge to produce a snap action. Typical constructions are shown in U.S. Pat. Nos. 3,628,215, 3,629,901, 3,933,271, 4,047,495 and 4,386,714.
In U.S. Pat. No. 4,638,916, a closure with a snap type hinge cap comprises a first part adapted to interengage with the open neck of a container, a second part forming a cap and an integral hinge interconnecting the first and second parts comprises a base wall and a peripheral skirt. A pair of hinge straps extends from the skirts and are positioned on opposite sides of the integral hinge. The radial length of the pair of hinge straps is less than the length of the arc through which the second cap part moves to and from and closed position relative to the first part such that the pair of straps stretch to function as springs. The ends of the pair of straps are attached to the skirts radially inwardly of the periphery of the skirts.
In U.S. Pat. No. 5,489,035, there is disclosed a closure with a snap type hinge cap which comprises a first part adapted to interengage with the open neck of a container, a second part forming a cap and an integral hinge interconnecting the first part and second part. Each of these parts comprises a base wall and a peripheral skirt. A pair of hinge straps extend from the skirts on opposite side of the integral hinge. The ends of the straps are straight and lie in substantially the same plane when the first part and second part in fully open position. Each strap has a portion intermediate the ends which extends out of the plane. Each strap is untensioned when the first part and second part are in fully open position. The intermediate portions of the straps extend axially in one direction. In one form, the intermediate portions of said straps are curved in cross section. In another form, intermediate portions of said straps are V-shaped in cross section.
Among the objectives of the present invention are to provide an improved closure with a snap-type hinge cap like that in U.S. Pat. No. 5,489,035 with improved performance and longer life; which further reduces or eliminates excessive stress on the straps during opening and closing which might cause breaking; and which can be made with minimal added cost.
In accordance with the invention, a closure with a snap type hinge cap comprises a first part adapted to interengage with the open neck of a container and a second part forming a cap. An integral hinge interconnects the first part and second part. Each of said parts comprises a base wall and a peripheral skirt. A pair of hinged straps are attached to the skirts and extend from the skirts on opposite side of said integral hinge. The end of the straps are straight and lie in substantially the same plane when the first part and second part are in fully open position. Each strap is stretched along its length during opening and closing of the first part and the second part. Each strap has a portion intermediate the ends which extends out of said plane when the first part and second part are in fully open position. Each strap has an intermediate portion which is thinner than the ends of the strap. Each strap is untensioned when the first part and second part are in fully open position. The intermediate portion of each strap extends axially downwardly or axially upwardly. In another form, the intermediate portion includes a transverse ledge or step at its ends. In a further form, the straps include a transverse ledge or strap and have the same thickness throughout.